CBSE Class 10 Physics Sources of Energy Worksheet Set C

Question. A solar water heater cannot be used to get hot water on :
(a) A sunny day
(b) A cloudy day
(c) A hot day
(d) A windy day
Answer : B

Question. Which of the following is not an example of a biomass energy source ?
(a) Wood
(b) Gobar gas
(c) Nuclear energy
(d) Coal
Answer : C

Question. Which of the following statement is false ?
(a) Biomass is derived from charcoal.
(b) In the presence of oxygen, biomass undergoes decomposition to form bio gas.
(c) Wind energy converts mechanical energy into electrical energy.
(d) Solar radiations are converted into electricity called solar energy.
Answer : B

Question. The inhalation of fumes and obnoxious smoke from coal mines causes which type of disease ?
(a) Pulmonary disease
(b) Coronary artery disease
(c) Hepatitis
(d) Liver cancer
Answer : A

Question. Carbon monoxide is an example of ________ .
(a) Primary pollutant
(b) Secondary pollutant
(c) Biodegradable pollutant
(d) Non - Biodegradable pollutant
Answer : A

Question.Match the following
Column I                                   Column II
(a) Rise of sea water                 (i) Geothermal energy
(b) Sea-wave energy                 (ii) Solar energy
(c) Energy form earth’s crust     (iii) Tidal energy
(d) Energy obtained from sum   (iv) Wane energy
Answer : (a) (iii), (b) (iv), (c) (i), (d) (ii).

Very Short Answers Type Questions

Question. If you could use any source of energy for heating your food which one would you prefer? State one reason for your choice. 
Answer : I would prefer a solar cooker for heating food because solar cooker is environmental friendly and causes no pollution.

Question. Though a hot iron emits radiations, yet it is not visible in the dark, why ?
Answer : Hot iron emits infra-red rays. These rays are invisible to the eyes.

Question. Name two forms of energy in which solar energy manifests itself in oceans.
Answer : (a) Tidal energy and (b) Ocean thermal energy.

Question. Which part of Sun’s energy is responsible for drying clothes and exposure to which part could be a health hazard ?
Answer : Infra-red (IR) radiations are responsible for drying clothes and ultraviolet (UV) radiations could be a health hazard.

Question. What do you mean by the term ‘thermal power plant’ ?
Answer : Thermal power plant is the power plant where coal is burnt to produce heat energy which is converted into electrical energy.

Question. Why does acid rain happen ?
Answer : Acid rain happens because of burning of fossil fuels which release oxides of carbon, nitrogen and sulphur in the atmosphere.

Question. ‘‘Burning fossil fuels is a cause of global warming.’’ Give reason in support of this statement.
Answer : Burning of fossil fuel produces CO₂, oxides of sulphur and nitrogen. CO₂ is a greenhouse gas, its excess produces greenhouse effect, increasing earth’s temperature and causes global warming.

Question. Name two constituents of biogas.
Answer : Two constituents of biogas are methane (CH₄) and Hydrogen .

Short Answers Type Questions

Question. What are solar cells ? Explain the structure of solar panel. List two principal advantages associated with solar cells. 
Answer : Solar cells are the devices which convert solar energy into electricity.
A simple solar cell is made up of sandwich of a siliconboron layer and a silicon-arsenic layer. Boron and arsenic are present in a very small amount. A piece of wire is soldered into the top of upper layer of cell and another piece of wire is soldered at the bottom of the lower layer to pass on the current. The solar cell is covered with a glass cover for protection.
Advantages :
(a) Solar cells have no moving parts.
(b) It requires less maintenance.

Question. While discussing about coal and petroleum a teacher told his students about PCRA’s (Petroleum Conservation Research Association) guidelines to save the fossil fuels while driving vehicles. Deepa was going to her school with her mother who was driving car. At the traffic signal, when the light was red, Deepa suggested her mother to switch off the engine. After reading the above passage, answer the following questions :
(a) Fossil fuels are natural resources, then why do we need to conserve them ?
(b) List any two ways of saving the fossil fuels.
Answer :
(a) Fossil fuels take millions of years in their formation, hence are exhaustible and need to be conserved to provide energy for a longer duration and sustainable development.
(b) Walking short distances or use of public transport.
Where possible switch off unnecessary lights.

Question. (a) Write Einstein’s mass-energy equation. Give the meaning of each symbol which occurs in it.
(b) In nuclear fission of a piece of uranium, 0.5 g of mass is lost, how much energy in MeV is obtained ?
Answer :
(a) According to Einstein, mass and energy are interchangeable and are related by the equation :
E = (Δm) c²
Here, Δm is the loss in mass in kg, c is the speed of light (3 × 108 ms^–1) and E is the energy in joule (J).
(b) Here, Δm = 0.5 g = 0.5 × 10–3 kg, c = 3 × 108 ms^–1 and
1 MeV = 1.6 × 10^–13 J
∴ Energy released, E = (Δm) c²
= [0.5× 10⁻³ ×(3 ×10⁸ )2]/ 1.6 10⁻¹³
4.5 ×1013/1.6 ×10⁻¹³ MeV
= 2.8 × 10²⁶ MeV

Long Answers Type Questions

Question. What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumptions ? 
Answer :
Environmental consequences of increasing demand for energy are as follows :
(a) Use of fossil fuels is increasing air pollution which is not good for our health.
(b) Air pollution is causing much damage to the ecosystem.
(c) Greenhouse effect has resulted in global warming which is manifesting itself in strange changes in the weather pattern around the world.
(d) Too much exploitation of fossil fuels is going to create a situation when there would be no fossil fuel.
Steps to reduce energy consumption :
(a) Use your household appliances efficiently.
(b) Use public transport instead of private modes of transport.
(c) Use bicycle whenever possible.
(d) Walk for short distance to commute.
(e) Avoid unnecessary use of modern gadgets which consume lot of energy.
(f) Get a solar water heater installed for winters.

Question. (a) What is a biogas plant ?
(b) Name five main parts of fixed dome type biogas plant.
(c) Draw a neat labelled diagram of a fixed dome type biogas plant.
Answer :
(a) The arrangement used for producing biogas from animal dung, human excreta, and domestic waste is known as biogas plant.
(b) A fixed dome type biogas plants consist of :
(i) Mixing tank : In this, slurry, animal dung and other waste materials are mixed.
(ii) Digester : It is a well like underground tank made up of bricks and cement. It has outlet and inlet valves. The roof of the digester is dome shaped. The dome acts as a storage tank of biogas. A gas outlet is fitted at the top of the dome.
(iii) Inlet chamber : It is situated on one side of the digester. It passes the slurry of cattle dung and other waste from the mixing tank to the digester.
(iv) Outlet chamber : It is on the other side of the digester. It is rectangular in shape and constructed with bricks and cement. It is connected to the overflow tank.
(v) Overflow tank : It collects the used slurry or spent slurry. This spent slurry can be used as manure.

Question. What are the merits and limitations of the energy that can be obtained from the deep inside the earth ?
Answer :
Merits of geothermal energy :
(a) It is a renewable source of energy.
(b) It involves low running cost.
(c) It does not create any pollution and help in creating clean environment.
(d) Maintenance cost of geothermal power plant is low.
(e) Geothermal power plants are unaffected by weather and night cycle day.
Limitations of geothermal energy :
(a) Geographically, there are very limited number of places where geothermal power plants are likely to operate effectively.
(b) Enhanced geothermal system can trigger earthquakes, therefore it affect land stability severly.
(c) High up front installation cost required for construction of geothermal power plant and its drilling wells, which requires advance technology.
(d) There is an abundance of greenhouse gases below the earth surface. They can might be escape through the holes drilled during constructions. It leads to global worming and acid rain.
(e) Geothermal Energy cannot be easily transported unlike other source of energy.

Case Study Based Questions

1. Answer question numbers 1(a) to 1(d) on the basis of your understanding of the following paragraph and the related studies concepts.
The Tehri dam is the highest dam in India and one of the highest in the World. The Tehri dam withholds a reservoir of capacity 4.0 km3 and surface area 52 km2. It is used for irrigation, municipal water supply and the generation of 1000 MW of hydroelectricity. The Tehri dam has been the object of protests. Environment activist Shri Sunder Lal Bahuguna led the “Anti Tehri Dam Movement” from 1980s to 2014. The protest was against the displacement of town inhabitants and environmental consequences of the weak ecosystem.The relocation of more than 1,00,000 people from the area has led to protracted legal battles over resettlement rights and ultimately resulted in the delayed completion of the project.

Question. How is hydropower harnessed ?
Answer : Hydro power plants convert the potential energy of water stored at great heights to kinetic energy of flowing water at high speed, then into electricity.

Question. Define 1 MW.
Answer : A megawatt is a unit for measuring power that is equivalent to one million watts. Megawatts are used to measure the output of a power plant or the amount of electricity (energy in per second) required by an entire city. One megawatt (MW) = 1,000 kilowatts = 1,000,000 watts.

Question. Mention two disadvantages of constructing Tehri Dam.
Answer : Major disadvantages of constructing dams are :
(i) People living in Tehri were relocated. They lost their farms and businesses.
(ii) The building of large dams can cause serious geological damage.

Question. What happens when water from great heights is made to fall on blades of turbine ?
Answer : When water from great height is made to fall on turbine it spins the motor of an electricity generator and creates a magnetic field that induces an electric current.
 

2. Read the following paragraph and answers the following questions :
Solar water heater consists of an insulated metallic box which is painted black from inside and outside In this box copper tubes painted black from outside and fitted in a zig-zag shape. The box and copper tubes are painted black so that they may absorb maximum radiant heat energy of the sun efficiently. The box in covered with a glass sheet lid to trap sun rays by producing greenhouse effect. The two ends of copper tubes are joined to a water storage tank as shown in figure, The solar water heater and its water storage tank are fitted on the roof of a building so that they may absorb the maximum radiant heat energy of the sun.

Question. Why metallic box is painted black from outside ?
Answer : Because black colour is good absorber of heat.

Question. What is meant by radiation here ?
Answer : The solar energy received is called radiation.

Question. Why copper tubes are used here ?
Answer : Because copper is good conductor of heat.

Question. What is greenhouse effect ?
Answer : The glass roof and glass walls of a greenhouse allow heat and sunlight to enter it but do not allow heat (infrared radiation) to escape on account of this greenhouse gets warmed.

3. The cost and security of energy and emissions of greenhouse gases (GHG) and other pollutants from the existing means of energy production are two main problems that have led to many technological developments in alternative energy sources. Using biomass to produce energy is one such alternative that has recently become attractive worldwide as a clean and sustainable source of energy. Anaerobic digestion (AD) is one of the preferred technologies for treating organic municipal solid waste (MSW) for the production of biogas and methane, which can be used as alternative fuel to liquid petroleum gas (LPG) and natural gas.

Question. Fossil fuels are
(a) Non-renewable source of energy
(b) Renewable source of energy
(c) Both (a) and (b)
(d) Neither (a) nor (b)
Answer : A

Question. Which of the following problem is associated with a burning of coal?
(a) Carbon-dioxide emission
(b) Acid rain
(c) Ash with toxic metal supurity
(d) All of these
Answer : D

Question. __________ is also called a biogas
(a) Biobutanol
(b) Biodiesel
(c) Bioethanol
(d) Biomethane
Answer : D

Question. Biogas is a better fuel than animal dung cake because
(a) Biogas has lower calorific value.
(b) Animal dung cake has high calorific value
(c) Biogas has high calorific value and leaves no residue
(d) Biogas is used as a fuel for cooking only whereas dung cake can be used for cooking,illuminant the lanterns.
Answer : C

Question. Which of the following organism produces biogas from cow drug sherry in the biogas plant?
(a) Aerobic bacteria
(b) Anaerobic bacteria
(c) Protozoa
(d) Fungi
Answer : B

4. Energy is the primary and most universal measure of all kinds work by human beings and nature. Everything what happens the world is the expression of flow of energy in one of its forms. Energy is the major input to drive the life cycle and improve it. Energy consumption is closely related to the progress of the mankind. The conventional sources of energy are generally non-renewable sources of energy, which are being used since a long time. These sources of energy are being used extensively in such a way that their known reserves have been depleted to a great extent. The sources of energy which are being produced continuously in nature and are in exhaustible are called non-conventional energy (or) renewable sources of energy.

Question. In order to make efficient solar cooker, the cover of cooker box should be made of:
(a) Transparent plastic sheet
(b) Shining aluminium sheet
(c) Butter paper sheet
(d) Transparent glass
Answer : D

Question. The process by which energy is produced in the sun is
(a) Nuclear fission
(b) Nuclear fusion
(c) Both nuclear fusion and fission
(d) Combustion of hydrogen
Answer : B

Question. The rise of sea-water during high tide is caused by the gravitational pull of the:
(a) Sun
(b) Earth
(c) Moon
(d) Mars
Answer : C

Question. In a hydroelectric power plant more electrical power can be generated if water falls from a greater height because:
(a) Its temperature increases.
(b) Larger amount of potential energy is converted into kinetic energy.
(c) The electricity content water increases with height.
(d) More water molecules dissociate into ions.
Answer : B

Question. Greenhouse effect in solar cooker is due to:
(a) Mirror
(b) Glass plate
(c) Outer cover
(d) Coating with black colour
Answer : A